Acrylonitrile polymer composition stabilized with acrolein, a phenol, and an inorganic acid, and method of making same



ACRYLONITRILE POLYMER COMPOSITION STA- BILIZED WITH ACROLEIN, A PHENOL, AND AN gNORGANIC ACID, AND METHOD OFMAKING Richard R. Holmes, Bethesda, Md., andLloyd T. Jenkins,

Decatur, Ala., assignors to The Chemstrand Corporation, Decatur, Ala., a corporation of Delaware No Drawing. Application May23,1 9 5,6 v

Serial No. 586,662

20 Claims. (Cl. 260-3245): I

containing at least 80 percent by Weight of polymerized into the product formed therefrom. Thiscoloralso develops in solutions upon standing for prolonged periods .of time.

The mechanism which causes color formation has not been definitely ascertained, although a variety. of reasons therefor have been advanced. The presence of. metal ions, such as iron, copper and manganese in the solutions may cause the'color. The employment ,of amide compounds as solvents may'result in formation vof amines when heat is-applied and cause color in the compositions.

Impurities present in the solvents havealso been cited as a cause. Whatever may be thereason for co lor formation, it results in compositions and products ofundesirable standards and therefore, hasbeen the sourceof concern, particularly in, commercial operations where such types of polymers or copolymers are employed.

Accordingly, it is an object of the,present invention to J prevent undesirable color formation in acrylonitrile poly mer compositions.

Another object is to minimize, color formation when solutions of the acrylonitrile polymers are permitted to :5,

stand for a prolonged period of t ime or upon application of heat. a

It is also an object of the invention, to prevent color formation in acrylonitrile polymers atelevated tempera;

tures. a

a A still further object of the inventionis theproduction of solutions of acrylonitrile polymers and articles produced therefrom having improved color characteristics.

Other objects and advantages will be -apparent from a consideration of the description of the invention which followshereafter. 1

In general, the objects of the invention are accomplished :by dissolving-the polymer of acryloniteile i n -a suitable solvent-therefor and preventing or; minimizing color formation by the prcsence in thesolut ion as an 2,878,207 Patented Mar. 17, 1959 '2 inhibiting agent, a combined reagent comprising acrolein, a compound having the general formula, t t-'t n-"'f wherein Ris hydrogen, methoxy, etlioxy or an OH group; and an inorganicacid having an ionization constant greater than, l X 10- 7 The components of the inhibiting agent may be employed in equal or unequalamounts, any one constituent being present in a range of from 98 to 1 percent in a three component system. The total amount of inhibiting agent may be employed in a range of about 0.3 to. 15 percent, based on the total polymer weight. However, it is preferred that the inhibiting agent of the instant invention be present in a small amount compared to the amount ofpolymer dissolved- Thus although the amount is not critical, it is preferred that the inhibiting agent be present in the'amount of about 0.3 to 3 percent, based on the total weight of the polymer. The inhibiting agent maybe added to the solvents before or after the polymer is dissolved therein. The inhibiting agent permits exposure to high temperatures for prolonged standing periods without thedevelopment of the objectionable color which usually resultsfin such solutions. The compositions of the instant inventionbmay be prepared in a varying temperature range. For example, the compositions of the instant invention may be prepared by mixing the polymer, a suitable solvent and the inhibiting agent at any temperature or heating the mixture to atemperature up to the boiling point of the solvent;

, Amongthe co mpbunds bearing'the general formula,

(I) on which may be ernploye d in practising the instant inventionare phenol, p-methoxy phenol, p-ethoxy phenol, hy- -droquinone,.etc,

Among the acids whichmay be employed inpractising the instant invention are sulfuric acid, nitric acid, phosphoric acid, hydrochloric. acid, etc.

Among, the;.so lvents, whi h may be used in practising the instant invention are N,N-dimethylformamide, N,N- dimethylz'acetamideaqueous zinc chloride,,sulfuric acid, .aqueous nitrieacid, aqueous sodium thiocyanate, ethylene carbonate, s ulf olane, nitromethane, etc I Thepolymeric materials, which may be employed in the practice of the present invention, are polyacrylonitrile, copolyirie'rs, including binary and ternary polymers containing at. Ieast SO percent. by weight pf acrylonitrile in ,the p o lym'er molecule, or a blend comprisingpolyacr'yloni; mile .or .copolyiriers. comprising acrylonitrile with from 2 toJO percentof anoth'enpolymeric material, the blend having .anoverall polymerizedacrylonitrile content of, at least perc'ent1by weight. .While the preferred polymers employed in the-instantinvention are'those" containing at least 1.80 ppe'rc'en't'v :of acrylonitrile, generally, recognized as the fiberjformiii laclryloriijt'ril'epolym'ers','it'will beunde'r is lie, ise applicable to polymers containing less than 80 percent acrylonitrile and the same stability is realized with the inhibiting agents defined herein. The acrylonitrile polymers containing less than 80 percent acrylonitrile are useful in forming films, coating compositions, molding operations, lacquers, etc., in all of which applications the alleviation of undesirable color is extremely important.

For example, the polymer may bea copolymer of from 80 to 98 percent acrylonitrile and from 2 to 20 percent of another monomer'containing the C==C link age and copolymerizable with acrylonitrile. Suitable monoolefinic monomers include acrylic, alpha-chloroacrylic and methacrylic acids; the acrylates, suchas methylmethacrylate, ethylmethacrylate, butylmethacrylate, methoxymethyl methacrylate, beta-chloroethyl methacrylate, and the corresponding esters of acrylic and alpha-chloroacrylic acids; vinyl chloride, vinyl fluoride, vinyl bromide, vinylidene chloride, l-chloro-l-bromoethylene; methacrylonitrile, acrylamide and methacrylpionat'e, and vinyl stearat'e; N-vinylimides, such as N" vinylphthalimide and N-vinylsuccinimide; methylene malonic esters; itaconic acid and itaconic ester; N-vinylcarbazole; vinyl furane; alkyl vinyl esters; vinyl sulfonic acid; ethylene alpha, beta-dicarboxylic acids or their anhydrides or derivatives, such as diethylcitraconf, diethylmesaconate, styrene, vinyl naphthalene; vinyl 's'ubstituted tertiary heterocyclic amines, such as the vinylpyridines and alkyl-substituted vinylpyridines, for example, 2-vinylpyridine, 4-vinylpyridine, Z-meth'yl-S-vinylpyi'idine, etc.; l-vinylimidazole and alkyl-substituted l-v'inylimidazoles, such as 2-, 4-, or S-methyl-l-vinylimidazole,' and other C==C containing polymerizable materials.

The polymer may be a ternary interpolymer, for example, products obtained by the interpolymerization of acrylonitrile and two or more of any of the monomers, other than acrylonitrile, enumerated above. More specifically, and preferably, the ternary polymer comprises acrylonitrile, methacrylonitrile, and 2-vin'ylpy ridine. The ternary polymers preferably contain from 80 to 9 7 percent of acrylonitrile, "from l to 10 percent or a vinylpyridine or a l-vinyli'mida'zole, and from 1 to 18 percent of another substance, such as methacrylonitrile or vinyl chloride.

The polymer may also be a blend of polyaeryloni'trile or of a binary interpolymer of from 80 to 99 percent acrylonitrile and from 1 to 20 percent of at least one other C=C containing substance with from 2 to 50 percent of the weight of the blend of a copolymer of from 10 to 70 percent of acrylonitrile and from 30 to 90 percent of at least one other C'=C containing polymerizable monomer. Preferably, when the polymeric material comprises a blend, it will be a blend of a copolymer of 90 to 98 percent acrylonitrile and from 2 to 10 percent of another mono-olefinic monomer, such as vinyl acetate, which is not receptive to "dyestufi, with a s'ufiicient amount of a copolymer of from 10 to 70 percent of acrylonitrile and from 30 to 90percent era viny1-substituted tertiary heterocyclic amine, such j as vinylpyridine or l-vinylimidazole, to give a dyeable blend having an overall vinyl-substituted tertiary heterocyclic amine con tent of from 2 to 10 percent, based on the weight of the blend.

The polymers, useful in the practice of the present invention, may bepr'epare'd by any conventional poly.- merization procedures, such as mass polymerization methods, solution polymerization methods, or aqueou emulsion procedures. However, the preferred ractice utilizes suspension polymerization wherein the polymer is prepared in finely divided form for immediate use in the fiber fabrication operations. The preferred suspension polymerization may utilize batch procedures, wherein monomers are charged with an aqueous see '4 taining the necessary catalyst and dispersing agents. A more desirable method involves the semi-continuous procedure in which the polymerization reactor containing the aqueous medium is charged with the desired monomers and the continuous withdrawal of polymer may also be employed.

The polymerization is catalyzed by means of any watersoluble peroxy compound, for example the potassium, ammonium and other water-soluble salts of peroxy acids, sodium peroxide, hydrogen peroxide, sodium perborate, the sodium salts of other peroxy acids, and any other water-soluble compound containing a peroxy group (00). A wide variation in the quantity of peroxy compound is possible. For example, from 0.1 to 3.0 percent by weight of the polymerizable monomer may be used. The catalyst may be charged at the outset of the reaction, or it may be added continuously or in increments throughout the reaction for the purpose of maintaining a more uniform concentration of catalyst in the reaction mass. The latter method is preferred because it tends to make the resultant polymer more uniform in its chemical and physical properties.

Although the uniform distribution of the reactants throughout the reaction mass can be achieved by vigorous agitation, it is generally desirable to promote the uniform distribution of reagents by using inert wetting agents, or emulsion stabilizers. Suitable reagents for this purpose are the water-soluble salts of fatty acids, such as sodium oleate and potassium stearate, mixtures of watersoluble fatty acid salts, such as common soaps prepared by the saponification of animal and vegetable oils, the amino soaps, such as salts of triethanolamine and dodecylmethylamine, salts of rosin acids and mixtures thereof, the water-soluble salts of half esters, of sulfuric acid and long chain aliphatic alcohols, sulfonated hydrocarbons, such as alkyl aryl sulfonates, and any other of a 'wide variety of wetting agents, which are in general or- 'ganic compounds containing both hydrophobic and hydrophilic radicals. The quantity of emulsifying agents will depend upon the particular agents selected, the ratio of monomer to be used, and the conditions of polymerization. In general, however, from 0.01 to 1.0 percent'by weight: of the monomers may be employed.

The emulsion polymerizations are preferably conducted in glass or glass-lined vessels which are provided with -a means for agitating the contents. I Generally rotary stirring devices are the most effective means of insuring the intimate contact of the reagents, but other methods maybe successfully employed,- for example by rocking or tumbling the reactors. The polymerization equipment generally used is-conventional in the art and the adaptation of a particular type of apparatus to the reaction contemplated is within the province of one skilled in the art. The articles manufactured therefrom may be produced by well-known conventional methods, 'for example, the wet-spinning, dry-spinning and meltspinning methods for producing fibers.

The following examples are illustrative rather than limitative and all parts, proportions and percentages are by Weight unless otherwise specified.

EXAMPLE I 7.5 grams of a polymer blend of 88 percent of a copolymer containing 94 percent of acrylonitrile and 6 percent of vinyl acetate and 12 percent of a copolymer of 50 percent of acrylonitrile and 50 percent of Z-methyl- S-vi-nyl pyridine were added to 45 milliliters of N,N-dirnethylacetamide containing approximately 0.05 gram of titanium dioxide. The mixture was stirred and heated to 70 C. It was then quickly cooled to room temperature and the color measured. This sample was used as aconnol. The purity is set forth below. Subsequently, like samples "were prepared but with 0.225 gram of a color inhibitor eontainin'g 0.075 gram each of acrolein, phenol and sulfuric acid; acrolein, 'p-niethoxy phenol and sulfuric acid; and acrolein, hydroquinone and sulfuric acid. The purity is set forth below.

Table I Inhibitor Percentage Purity Used A Control 7. 0 Acroleln, Phenol and Sulfuric Acid 3 7. 4 Acroleln, -Methoxy Phenol and Sulfuric Acid- 8 7. 3 Acroleln, ydroqulnone and Sulfuric Acid.... .4. 1

EXAMPLE; 11

sulfuric acid; acrolein, p-methoxy phenol and sulfuric acid; and acrolein, hydroquinone and sulfuric acid. The purity is set forth below Table II Inhibitor Perrtjenzsiage Purity Control Acrolein, Phenol and Sulfuric Acid.. 3 Acroleimp-Methoxy Phenol and Sulfur Acid. 3 Acrolein, Hydroquinone and Sulfuric Acid 3 EXAMPLE III 7.5 grams of an acrylonitrile homopolymer were added to 45 millilitersof N,N-dimethylacetamide containing approximately 0.05 gram of titanium dioxide. The mixture was stirred and heated for 50 minutes at 90 C. It was then quickly cooled to room temperature and the color measured. This sample was used as a control. The purity of the control sampleis set forth below. Subsequently, like samples were prepared but with 0.225 gram of an inhibiting agent containing 0.075 gram each of acrolein, phenol and sulfuric acid; acrolein, p-methoxy phenol and sulfuric acid; and acrolein, hydroquinone and sulfuric acid. The purity is set forth below.

Table III Inhibitor Percentage Purity Used The tests for color indicative of approaching whiteness used throughout the examples consist of measurements of purity as calculated from the tristimulus values determined on a General Electric spectrophotometer by the methods recommended by the Standard Observer and Coordinate System of the International Commission on Illumination, as fully set forth in the Handbook of Colorirnetry published by The Technology Press, Massachusetts Institute of Technology in 1936.

The compositions of the instant invention present many advantages. For example, products formed from the polymer solutions of the instant invention are free of objectionable color and therefore of greater commercial value. In preparing the polymer solutions, heat may be applied without the danger of color formation and the solutions, if necessary, may stand for prolonged periods and remain free of color. The inhibiting agents are '6 readily available and inexpensive. Therefore, no great increase in production cost is necessary. The compositions containing the inhibitors may be prepared without going through detailed and elaborate procedures that necessitate expensive changes in the design of the apparatus used to manufacture them.

It will be understood to those skilled in the art that many apparently widely different embodiments of this invention can be made without departing from the spirit and scope thereof. Accordingly, it is to be understood that this invention is not to be limited to the specific embodiments thereof except as defined in the appended claims.

We claim:

l. A new composition of matter comprising a polymer containing at least percent of polymerized acrylonitrile and up to 20 percent of another polymerizable monoolefinic monomer copolymerizable therewith, a solvent therefor, and an inhibiting agent containing substantially equal proportions by weight of acrolein, a compound having the general formula,

wherein R is selected from the group consisting of hydrogen, methoxy, ethoxy, and hydroxyl groups; and an inorganic acid having an ionization constant greater than 1x10 2. A new composition of matter as defined in claim 1 wherein the polymer is a copolymer containig from 80 to 98 percent of acrylonitrile and from 2 to 20 percent of another polymerizable mono-olefinic monomer copolymerizable therewith.

3. A new composition of matter as defined in claim 1 wherein the polymer is a blend of 80 to 99 percent of (A) a copolymer containing to 98 percent of acrylonitrile and 2 to 10 percent of vinyl acetate and l to 20 percent of (B) a copolymer containing 10 to 70 percent of acrylonitrile and 30 to 90 percent of 2-methyl-5-vinyl pyridine.

4. A new composition of matter as defined in claim 1 wherein the polymer is polyacrylonitrile.

5. A new composition of matter as defined in claim 1 wherein the compound is phenol.

6. A new composition of matter as defined in claim 1 wherein the compound is p-methoxy phenol.

7. A new composition of matter as defined in claim 1 wherein the compound is p-ethoxy phenol.

8. A new composition of matter as defined in claim 1 wherein the compound is hydroquinone.

9. A new composition of matter as defined in claim 1 wherein the solvent is N,N-dimethylacetamide.

10. A new composition of matter comprising a copolymer containing 80 to 98 percent of acrylonitrile and 2 to 20 percent of vinyl acetate, a solvent therefor, and 0.3 to 15 percent, based on the total Weight of the polymer, of an inhibiting agent, said inhibiting agent containing substantially equal proportions by weight of acrolein, a compound having the general formula,

wherein R is selected from the group consisting of hydrogen, methoxy, ethoxy, and hydroxyl groups; and sulfuric acid.

wherein R is selected from the group consisting of hydrogen, methoxy, ethoxy, and hydroxyl groups; and sulfuric acid.

12. A new composition of matter comprising polyacrylonitrile, a solvent therefor, and 0.3 to 15 percent, based on the total weight of the polymer, of an inhibiting agent, said inhibiting agent containing substantially equal proportions by weight of acrolein, a compound having the general formula,

wherein R is selected from the group consisting of hydrogen, methoxy, ethoxy, and hydroxyl groups; and sulfuric acid.

13. A method for preparing a new composition of matter comprising mixing a polymer containing at least 80 percent of polymerized acrylonitrile and up to 20 percent of another polymerizable mono-olefinic monomer copolymerizable therewith, a solvent therefor, and an inhibiting 8 agent containing substantially equal proportions by weight of acrolein, a compound having the general formula,

wherein R is selected from the group consisting of hydrogen, methoxy, ethoxy, and hydroxyl groups; and an inorganic acid having an ionization constant greater than 1X 10- and heating the mixture at a temperature in a range of 25 C. to the boiling .point of the mixture to fonn a homogeneous solution.

14. The method as defined in claim 13 wherein the polymer is a copolymer containing from to 98 .percent of acrylonitrile and from 2 to 20 percent of another polymerizable mono-olefinic monomer copolymerizable therewith.

15. The method as defined in claim 13 wherein the polymer is a blend of 80 to 99 percent of (A) a copolymer containing to 98 percent of acrylonitrile and 2 to 10 percent of vinyl acetate and l to 20 percent of (B) a copolymer containing 10 to 70 percent of acrylonitrile and 30 to 90 percent of Z-methyl-S-vinyl pyridine.

16. The method as defined in claim 13 wherein the polymer is polyacrylonitrile.

17. The method as defined in claim 13 wherein the compound is phenol.

18. The method as defined in claim 13 wherein the compound is p-methoxy phenol.

19. The method as defined in claim 13 wherein the compound is p-ethoxy phenol.

20. The method as defined in claim 13 wherein the compound is hydroquinone.

References Cited in the file of this patent UNITED STATES PATENTS 2,502,030 Scheiderbauer Mar. 28, 1950 2,624,722 Kropa et al. Jan. 6, 1953 2,730,436 Young et al. Jan. 10, 1956 

1. A NEW COMPOSITION OF MATTER COMPRISING A POLYMER CONTAINING AT LEAST 80 PERCENT OF POLUMERIZED ACRYLONITRILE AND UP TO 20 PERCENT OF ANOTHER POLYMERIZABLE MONOOLEFINIC MONOMER COPOLYMERIZABLE THEREWITH, A SOLVENT THEREFOR, AND AN INHIBITING AGENT CONTAINING SUBSTANTIALLY EQUAL PROPORTIONS BY WEIGHT OF ACROLEIN, A COMPOUND HAVING THE GENERAL FORMULA, 